A Computational Analysis of Flow Field in Twin-Track Subway Tunnel to Improve Air Quality

2013 ◽  
Vol 319 ◽  
pp. 599-604
Author(s):  
Makhsuda Juraeva ◽  
Kyung Jin Ryu ◽  
Sang Hyun Jeong ◽  
Dong Joo Song
Keyword(s):  
Air Quality ◽  
Computational Model ◽  
Stokes Equations ◽  
Ventilation System ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Subway Tunnel ◽  
Air Supply ◽  
And Performance

A computational model of existing Seoul subway tunnelwas analyzed in this research. The computational model was comprised of one natural ventilationshaft, two mechanical ventilationshafts, one mechanical airsupply, a twin-track tunnel, and a train. Understanding the flow pattern of the train-induced airflow in the tunnel was necessary to improve ventilation performance. The research objective wasto improve the air quality in the tunnel by investigating train-induced airflow in the twin-track subway tunnel numerically. The numerical analysis characterized the aerodynamic behavior and performance of the ventilation system by solving three-dimensional turbulent Reynolds-averaged Navier-Stokes equations. ANSYS CFX software was used for the computations. The ventilation and aerodynamic characteristics in the tunnel were investigated by analyzing the mass flowrateat the exits of the ventilation mechanicalshafts. As the train passed the mechanical ventilation shafts, the amount of discharged-air in the ventilationshafts decreased rapidly. The air at the exits of the ventilation shafts was gradually recovered with time, after the train passed the ventilation shafts. The developed mechanical air-supply for discharging dusty air and supplying clean airwas investigated.The computational results showed that the developed mechanical air-supplycould improve the air quality in the tunnel.

scholarly journals Numerical Investigation on Flapping Aerodynamic Performance of Dragonfly Wings in Crosswind

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Chao Wang ◽  
Rui Zhang ◽  
Chaoying Zhou ◽  
Zhenzhong Sun
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Lateral Force ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Sideslip Angle ◽  
Flight Direction ◽  
Time Average ◽  
Dragonfly Wings

Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angle ϑ between the crosswind and the flight direction varied from 0o to 90o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angle ϑ has a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angle ϑ on each dragonfly wing are different, e.g., ϑ has a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

Numerical simulation of dispersion and distribution behaviors of hydrogen leakage in the garage with a crossbeam

SIMULATION ◽  
2019 ◽  
Vol 95 (12) ◽  
pp. 1229-1238 ◽  
Author(s):  
Yunhao Li ◽  
Juncheng Jiang ◽  
Yuan Yu ◽  
Qingwu Zhang
Keyword(s):  
Mole Fraction ◽  
Natural Ventilation ◽  
Stokes Equations ◽  
Ventilation System ◽  
Three Dimensional ◽  
Dynamics Simulation ◽  
Navier Stokes ◽  
Explosion Hazard ◽  
Safety Issues ◽  
Set Up

A three-dimensional computational fluid dynamics simulation model resolved by the unsteady Reynolds-Averaged Navier–Stokes equations was developed to predict hydrogen dispersion in an indoor environment. The effect of the height of the crossbeam (Hc) on hydrogen dispersion and distribution behaviors in a four-car garage was numerically investigated under fully confined and natural ventilation conditions. For the fully confined condition, the garage was almost completely filled with a flammable hydrogen cloud at t=600 s. In addition, the volumetric ratio of the flammable region, thickness of the hydrogen stratification, and hydrogen mole fraction all increased as Hc increased. When two symmetric ventilation openings were set up, the volumetric ratio of the flammable region decreased by 50% at t=600 s. Moreover, Hc had evident influence on the vertical distribution of hydrogen mole fraction. In addition, there existed little explosion hazard under the height of 1.6 m. The results show that Hc was a non-negligible factor for the safety design of hydrogen in the garage and Hc=0.12 m was the optimal height of the crossbeam. Furthermore, the ventilation system in the present study cannot completely eliminate the risk of hydrogen explosion. The present risk assessment results can be useful to analyze safety issues in automotive applications of hydrogen.

scholarly journals Experimental and numerical research of the influence of thrust vector control on the missile aerodynamics by cold and hot jet simulations

2020 ◽  
Vol 48 (4) ◽  
pp. 770-778
Author(s):  
Goran Ocokoljić ◽  
Boško Rašuo ◽  
Dijana Damljanović ◽  
Saša Živković
Keyword(s):  
Vector Control ◽  
Three Dimensional ◽  
Combustion Products ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Cfd Model ◽  
Thrust Vector Control ◽  
Thrust Vector ◽  
And Performance ◽  
Definition Of

The flow field phenomena that occur as a result of thrust vector control (TVC) system activity on a missile with lateral jets are very complex and influence all other components of the missile. Influence is more significant when TVC is generating commands, when jets are asymmetrically directed. The main goal of these study was to determine the influence of of the hot rocket motor's combustion products on the basis of the CFD model proven with the cold-jet simulation. Based on obtained experimental aerodynamic coefficients for the cold-jet simulation the preliminary aerodynamic CFD model was designed. Three-dimensional Reynolds averaged Navier-Stokes numerical aerodynamic and hot-jet simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. The study resulted in the definition of a methodology for the investigation of the jet reaction effects in a wind tunnel. A method for determining of the TVC system interference on the aerodynamic characteristics, as a basic prerequisite for structural, stability and performance analysis, was proposed. Mutual verification and validation process was carried out through experiment and proper application of the commercial CFD software code for calculation aerodynamic effects of the hot gases lateral jets on the performance of a guided missile. Experimental and computational results of the pitching moment coefficients are presented and agreed well with.

Design and performance study of a parametric diverterless supersonic inlet

2019 ◽  
Vol 234 (2) ◽  
pp. 470-489
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Operational Mode ◽  
Performance Study ◽  
Navier Stokes Equations ◽  
Supersonic Inlet ◽  
Wetted Area ◽  
And Performance

Diverterless supersonic inlet integration for a flight vehicle requires a three-dimensional compression surface (bump) design with an acceptable shock structure and boundary layer diversion; this results in a low drag induction system with acceptable propulsive efficiency. In this investigation, a computational fluid dynamics-based-generated bump is used to design an integrated diverterless supersonic inlet without any bleed mechanism on a forebody with a large wetted area. Numerical solution of the Navier–Stokes equations simulates the flow pattern of the configuration. The forebody design analysis includes simulating the effects of angle of attack and sideslip by dependent computational domains. Results demonstrate the ability of the bump surface to keep the shock structures in an operational mode even at high supersonic angles of attack. Analysis of shock structures and shock wave boundary layer interactions at supersonic maneuver conditions indicate that the aerodynamic efficiency of the diverterless supersonic inlet in conditions with a thick boundary layer and high angles of attack is sufficient to ensure operation throughout the supersonic flight envelope.

Unsteady Aerodynamic Characteristics of a High Speed Train with Crosswind

2011 ◽  
Vol 66-68 ◽  
pp. 1878-1882
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Chen Guang Fan ◽  
Li Lu
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
High Speed ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Vehicle Speed ◽  
High Speed Train ◽  
Mesh Method

The aerodynamic performances of a high speed train will significant change under the action of the crosswind. Large eddy simulation (LES) was made to solve the flow around a simplified CRH2 high speed train with 250km/h and 350km/h under the influence of a crosswind with 28.4m/s base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of static train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field around train is completely different between Wind tunnel experiment and factual running. Many vortices will be produced on the leeside of the train with alternately vehicle bottom and back under the influence of a crosswind. The flow field around train is similar with different vehicle speed.

Computational Analysis of Aerodynamics and Thermodynamics for the X-51 High-Velocity Aircraft

2020 ◽  
pp. 41-57
Author(s):  
P.V. Silvestrov ◽  
S.T. Surzhikov
Keyword(s):  
High Velocity ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Distribution Patterns ◽  
Aerodynamic Characteristics ◽  
Convergence Time ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Thermally Conductive ◽  
Spatial System

The paper presents a numerical investigation of aero-dynamic coefficients for a model of an X-51-type high-velocity aircraft moving at Mach 6. The simulation made use of the original and modified versions of our custom hydrocodes (UST3D and UST3D-AUSMPW) designed for numerical simulation of aerodynamics and thermodynamics in high-velocity aircraft of arbitrary shapes. Such hydrocodes implement a model of viscous compressible thermally conductive gas described by a non-steady-state spatial system of Navier --- Stokes equations solved over unstructured three-dimensional tetrahedral meshes. The paper considers the theoretical aspects of simulating the aerodynamics and thermodynamics of high-velocity aircraft numerically. We describe the method for computing mass flow through mesh cell boundaries implemented in the modified custom hydrocode version. We performed cross-validation of the results obtained using our custom hydrocodes and compared our hydrocodes in terms of result convergence time. We show that these custom hydrocodes ensure adequately accurate distribution patterns concerning the fields of the values sought, and provide high-precision computation of aerodynamic characteristics as compared to each other

Design Optimization of a Centrifugal Fan with Splitter Blades

2015 ◽  
Vol 32 (2) ◽  
Author(s):  
Man-Woong Heo ◽  
Jin-Hyuk Kim ◽  
Kwang-Yong Kim
Keyword(s):  
Stokes Equations ◽  
Reference Model ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Latin Hypercube Sampling ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Multi Objective ◽  
Design Variables

AbstractMulti-objective optimization of a centrifugal fan with additionally installed splitter blades was performed to simultaneously maximize the efficiency and pressure rise using three-dimensional Reynolds-averaged Navier-Stokes equations and hybrid multi-objective evolutionary algorithm. Two design variables defining the location of splitter, and the height ratio between inlet and outlet of impeller were selected for the optimization. In addition, the aerodynamic characteristics of the centrifugal fan were investigated with the variation of design variables in the design space. Latin hypercube sampling was used to select the training points, and response surface approximation models were constructed as surrogate models of the objective functions. With the optimization, both the efficiency and pressure rise of the centrifugal fan with splitter blades were improved considerably compared to the reference model.

Aerodynamic Performance Analysis of a Bobsleigh Body Shape

2015 ◽  
Author(s):  
Hyeon-Seok Shim ◽  
Hyo-Yeon Jung ◽  
Kwang-Yong Kim
Keyword(s):  
Drag Coefficient ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Major Axis ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Optimal Number ◽  
Navier Stokes ◽  
Computational Domain ◽  
Axis Length

Aerodynamic performance of a bobsleigh is one of the most important factors in reducing the race time. In this study, an investigation on the aerodynamic characteristics of a bobsleigh has been performed using three-dimensional Reynolds-averaged Navier-Stokes equations with the k-ε turbulence model. An unstructured tetrahedral grid system was constructed in the computational domain, and the optimal number of grids was selected through a grid-dependency test. The major axis length and thickness of ellipse-shaped front bumper, and the radii of the cowling on side and front views, were selected as four geometric parameters to be tested, and the drag coefficient was considered as an aerodynamic performance parameter. It was found that the drag coefficient was more sensitive to the thickness of the front bumper and the radius of the cowling on side view of the bobsleigh than on the other parameters.

Numerical Simulation and Experiment Research on Aerodynamic Characteristics of a Multi-Blade Centrifugal Fan

2011 ◽  
Vol 317-319 ◽  
pp. 2157-2161
Author(s):  
Yong Chao Zhang ◽  
Qing Guang Chen ◽  
Yong Jian Zhang ◽  
Xiang Xing Jia
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Cfd Method

The full flow field model of a widely used multi-blade centrifugal fan was built, and unstructured grids were used to discrete the computational domain. The moving reference frame is adopted to transfer data between the interfaces of the rotating field and the stationary field. Pressure boundary conditions are specified to the inlet and the outlet. The SIMPLE algorithm in conjunction with the RNG k-ε turbulent model was used to solve the three-dimensional Navier-Stokes equations. The steady and unsteady numerical simulations of the inner flow in the fan at different working conditions were presented using the CFD method. The numerical simulation results were validated by contrasting to the experiment results. The results displayed the characteristics of the velocity field, pressure field, pressure fluctuation at two monitoring points in the centrifugal fan. The results can provide basis for optimizing the fan design and the internal flow, and have important value of engineering applications in the increase of the overall performance in operation.

Modelling the Flow Around Airfoils Equipped with Vortex Generators Using a Modified 2D Navier–Stokes Solver

2005 ◽  
Vol 127 (2) ◽  
pp. 223-233 ◽  
Author(s):  
I. G. Nikolaou ◽  
E. S. Politis ◽  
P. K. Chaviaropoulos
Keyword(s):  
Turbulent Flows ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Vortex Generators ◽  
Navier Stokes ◽  
Complex Flow ◽  
Wind Turbine Blades ◽  
Production Term

Vortex generators (VGs) are commonly used for trimming the aerodynamic and aeroelastic performance of wind turbine blades by delaying flow separation. There is therefore a need for the development of reliable, still computationally affordable, models for blade designers to use to predict and enhance the aerodynamic characteristics of airfoils equipped with VGs. Such a model is proposed in the present paper, addressing in particular near-stall and post-stall airfoil performance. Starting from the three-dimensional Navier–Stokes equations that essentially describe the complex flow around a blade/VG configuration, a spanwise averaging procedure is applied, resulting in an equivalent set of two-dimensional equations, enriched with extra source terms. These terms are modelled using elementary vortex flow theory. In turbulent flows, the production term of the turbulent kinetic energy is also augmented by the vorticity induced by the VG. The model is evaluated by studying the flow past a blade section with and without VGs. An analysis of the performance of nine alternative VG configurations is also presented to demonstrate the sensitivity of the airfoil polars to the VG geometric parameters.

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